CN111548834B - Coke powder pretreatment process for sintering, iron ore sintering process and system - Google Patents

Coke powder pretreatment process for sintering, iron ore sintering process and system Download PDF

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CN111548834B
CN111548834B CN201910111175.2A CN201910111175A CN111548834B CN 111548834 B CN111548834 B CN 111548834B CN 201910111175 A CN201910111175 A CN 201910111175A CN 111548834 B CN111548834 B CN 111548834B
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stage cylinder
powder
coke powder
lime milk
rotating shaft
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CN111548834A (en
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王兆才
周志安
胡兵
刘克俭
李康
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Zhongye Changtian International Engineering Co Ltd
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Zhongye Changtian International Engineering Co Ltd
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    • C—CHEMISTRY; METALLURGY
    • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
    • C10L—FUELS NOT OTHERWISE PROVIDED FOR; NATURAL GAS; SYNTHETIC NATURAL GAS OBTAINED BY PROCESSES NOT COVERED BY SUBCLASSES C10G, C10K; LIQUEFIED PETROLEUM GAS; ADDING MATERIALS TO FUELS OR FIRES TO REDUCE SMOKE OR UNDESIRABLE DEPOSITS OR TO FACILITATE SOOT REMOVAL; FIRELIGHTERS
    • C10L5/00—Solid fuels
    • C—CHEMISTRY; METALLURGY
    • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
    • C10L—FUELS NOT OTHERWISE PROVIDED FOR; NATURAL GAS; SYNTHETIC NATURAL GAS OBTAINED BY PROCESSES NOT COVERED BY SUBCLASSES C10G, C10K; LIQUEFIED PETROLEUM GAS; ADDING MATERIALS TO FUELS OR FIRES TO REDUCE SMOKE OR UNDESIRABLE DEPOSITS OR TO FACILITATE SOOT REMOVAL; FIRELIGHTERS
    • C10L5/00—Solid fuels
    • C10L5/02—Solid fuels such as briquettes consisting mainly of carbonaceous materials of mineral or non-mineral origin
    • C10L5/04—Raw material of mineral origin to be used; Pretreatment thereof
    • C—CHEMISTRY; METALLURGY
    • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
    • C10L—FUELS NOT OTHERWISE PROVIDED FOR; NATURAL GAS; SYNTHETIC NATURAL GAS OBTAINED BY PROCESSES NOT COVERED BY SUBCLASSES C10G, C10K; LIQUEFIED PETROLEUM GAS; ADDING MATERIALS TO FUELS OR FIRES TO REDUCE SMOKE OR UNDESIRABLE DEPOSITS OR TO FACILITATE SOOT REMOVAL; FIRELIGHTERS
    • C10L5/00—Solid fuels
    • C10L5/40—Solid fuels essentially based on materials of non-mineral origin
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22B—PRODUCTION AND REFINING OF METALS; PRETREATMENT OF RAW MATERIALS
    • C22B1/00—Preliminary treatment of ores or scrap
    • C22B1/14—Agglomerating; Briquetting; Binding; Granulating
    • C22B1/16—Sintering; Agglomerating
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22B—PRODUCTION AND REFINING OF METALS; PRETREATMENT OF RAW MATERIALS
    • C22B1/00—Preliminary treatment of ores or scrap
    • C22B1/14—Agglomerating; Briquetting; Binding; Granulating
    • C22B1/24—Binding; Briquetting ; Granulating
    • C22B1/242—Binding; Briquetting ; Granulating with binders
    • C22B1/243—Binding; Briquetting ; Granulating with binders inorganic
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E50/00—Technologies for the production of fuel of non-fossil origin
    • Y02E50/30—Fuel from waste, e.g. synthetic alcohol or diesel

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  • Organic Chemistry (AREA)
  • Engineering & Computer Science (AREA)
  • Geochemistry & Mineralogy (AREA)
  • Geology (AREA)
  • General Life Sciences & Earth Sciences (AREA)
  • Environmental & Geological Engineering (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Oil, Petroleum & Natural Gas (AREA)
  • Manufacturing & Machinery (AREA)
  • Materials Engineering (AREA)
  • Mechanical Engineering (AREA)
  • Metallurgy (AREA)
  • Inorganic Chemistry (AREA)
  • Manufacture And Refinement Of Metals (AREA)

Abstract

The invention provides a coke powder pretreatment process for sintering, which comprises the following steps: 1) conveying quicklime into a first-stage cylinder, spraying water into the first-stage cylinder, and digesting the quicklime in the first-stage cylinder to obtain lime milk; 2) conveying the lime milk obtained in the step 1) into a second-stage cylinder, conveying coke powder and fine iron powder into the second-stage cylinder, and mixing the lime milk, the coke powder and the fine iron powder in the second-stage cylinder to form a fuel structure taking the coke powder as a core, forming lime milk slurry and coating the fine iron powder. So as to improve the combustion environment of the solid fuel in the sintering process of the coke powder, reduce the oxygen potential in the peripheral gas film during the combustion of the coke powder and inhibit the oxidation of N element in the fuel to NOx(ii) a On the other hand, a calcium ferrite substance is quickly formed on the surface of the coke powder to promote the reverse reduction of the generated NOx to N2。

Description

Coke powder pretreatment process for sintering, iron ore sintering process and system
Technical Field
The invention relates to a coke powder pretreatment process for sintering, a novel sintering process and a system, in particular to a sintering-based low-NO processxA burning coke powder pretreatment process, a novel sintering process and a system adopting the pretreated coke powder, belonging to the field of sintering.
Background
The sintering process is a main flow of processing the iron and steel smelting furnace burden in China due to the advantages of large production scale, strong resource adaptability, low production cost and the like. The sintering process is also a high-energy-consumption and high-pollution centralized link in the steel smelting process, the amount of discharged waste gas accounts for about half of the total waste gas amount in the steel industry, and the waste gasSO in gasx、NOxAnd the emission of pollutants such as persistent organic matters and the like all dominates the first place of the steel industry. With the issuance and implementation of laws and regulations and relevant policies such as the air pollution prevention action plan, the new environmental protection law with the most strict history, the steel sintering and pellet industry air pollutant emission standard and the like, higher requirements are put forward on the emission index control of sintering pollutants. According to the current standard requirement, all sintering machines execute SO2The concentration is 200mg/m3NOx concentration 300mg/m3Emission limits of (2) are more stringent, e.g. NO in industrial furnaces of ShanghaixThe emission limit is 200mg/m3. In the proposal of the emission standard of atmospheric pollutants in the iron and steel sintering and pelletizing industry, published by the ministry of environmental protection in 2017, the emission of each pollutant is further greatly reduced, and SO is required under the standard condition that the oxygen content in flue gas is 16 percent2Emission concentration of less than 30mg/m3，NOxEmission concentration of less than 100mg/m3。
The development of the single flue gas desulfurization technology is mature up to now, the desulfurization efficiency reaches more than 90 percent, the emission reaches the standard, and the pursuit aims are only how to further reduce the investment and the operation cost, improve the operation reliability and the automation level and expand the byproduct recycling way. For NOx treatment, a flue gas denitration technology which is applied more at home and abroad and has a relatively mature technology is a Selective Catalytic Reduction (SCR) method, the denitration rate can reach 90%, but the temperature of sintering flue gas is only 130-150 ℃, which is far lower than the appropriate reaction temperature required by the SCR technology, which is 320-450 ℃, a large amount of energy is consumed to heat the flue gas, the operation cost is high, and the problem of secondary pollution caused by catalyst failure exists. It is worth noting that the activated carbon flue gas purification technology capable of realizing multi-pollutant cooperative treatment is widely accepted in the industry and has been successfully applied to large-scale sintering plants such as steel, exquisite steel, and Tai steel. The sulfur dioxide removal rate can reach 95% regardless of the single-tower design or the double-tower design, and for nitrogen oxides, the denitration rate of the single-tower design is less than 60%, and although the denitration rate of the double-tower design can be further improved to more than 85%, the investment cost is correspondingly increased greatly.
By adopting the scheme of the prior art, NO in the flue gas of the sintering machine in ChinaxThe concentration is usually between 200 and 350mg/m3At the edge of the limit value of the current national emission standard, most sintering plants are only provided with a flue gas desulfurization system based on economic consideration, and the environmental protection standard can be reached only by replacing the limit value with the environmental protection standard value under the environment-friendly high pressure. If the process can be controlled, NO in the flue gas can be ensuredxThe generated concentration is reduced by 10-20 percent and is within the warning line, so that the fundamental contradiction between emission standard reaching and high-efficiency production is thoroughly solved. In the coming years, along with the formal implementation of new emission standards, a denitration system and a desulfurization system become standard preparations for sintering flue gas purification, and an activated carbon flue gas purification technology capable of realizing multi-pollutant cooperative treatment is also selected by various large sintering plants as a first choice. For the sintering plant which is currently planning and building the activated carbon flue gas purification device, the single tower type design with low investment cost is faced, but the purified flue gas NO isxThe discharge concentration is still higher than 100mg/m3And double tower type design purified flue gas NOxThe discharge concentration can reach the standard, but the investment cost is high.
Disclosure of Invention
Research of experts and scholars in the industry indicates that: NO in flue gas of sintering processxMainly of the fuel type NOx，NOxMore than 95% of the N element is derived from fuel. On one hand, the method improves the combustion environment of solid fuel (such as coke powder) in the sintering process, reduces the oxygen potential in the peripheral gas film when the coke powder is combusted, and is favorable for reducing N element in the fuel to NOxThe conversion of (a); on the other hand, the product of the sintering process, calcium ferrite, can be used as a catalyst to promote NOxTo N2Is helpful for timely processing the generated NOxEffecting inhibition of NOxThe amount of discharge of (c). If the advantages of process control and tail end treatment can be combined at the same time, the NO of the flue gas is firstly reducedxThe concentration is generated, and a single-tower type active carbon flue gas purification device is used as an auxiliary, so that the worries of the rear trouble can be solved. In conclusion, from the process perspective, a low NO is developedxThe sintering process control technology is very important for the sustainable development of the sintering industry.
In view of the above-mentioned drawbacks of the prior art,the invention aims to provide a coke powder pretreatment process, which utilizes lime milk with extremely strong viscosity generated by over-digestion of quicklime to carry out surface pretreatment on coke powder with poor hydrophobicity, and a small amount of fine iron powder is adhered to the surface of the coke powder to form a fuel structure taking the coke powder as a core, hanging lime milk and coating the fine iron powder. So as to improve the combustion environment of the solid fuel in the sintering process of the coke powder, reduce the oxygen potential in the peripheral gas film during the combustion of the coke powder and contribute to reducing the content of N element to NO in the fuelxThe conversion of (a).
Another object of the invention is: and uniformly mixing and granulating the pretreated coke powder and the sintering mixture, and conventionally sintering the pelletized pellets. The coke powder pretreated by the method is coated with a layer of lime milk and iron ore powder on the outer surface, and a calcium ferrite product is rapidly generated during combustion, so that NO is promotedxConversion to N2Reduction of NOxThe amount of production of (c).
Through experimental research, after the system is adopted to pretreat the coke powder, the pretreated coke powder is used for sintering iron ore and sintering NO in flue gasxThe generation amount and concentration of the nitrogen oxide are reduced by 20-40%, and the process control of sintering flue gas low nitrogen oxide can be realized.
According to a first embodiment of the present invention, there is provided a process for pretreating coke powder for sintering.
A coke powder pretreatment process for sintering comprises the following steps:
1) conveying quicklime into a first-stage cylinder, spraying water into the first-stage cylinder, and digesting the quicklime in the first-stage cylinder to obtain lime milk;
2) conveying the lime milk obtained in the step 1) to a second-stage cylinder, and conveying coke powder and fine iron powder to the second-stage cylinder; the lime milk, the coke powder and the fine iron powder are mixed in the second-stage cylinder to form a fuel structure taking the coke powder as a core, hanging the lime milk into slurry and coating the fine iron powder.
Preferably, the first-stage cylinder has a first rotary shaft provided therein. The first rotating shaft is provided with blades. The first rotation shaft rotates clockwise (or counterclockwise). The quicklime and water are stirred and mixed by the blades on the first rotating shaft. The quicklime and the water are slaked and mixed in the first-stage cylinder, and simultaneously, the quicklime and the water are conveyed towards the discharge port of the first-stage cylinder.
Preferably, the second stage cylinder in step 2) is disposed directly below the first stage cylinder. The direction of the first-stage cylinder for conveying the materials is opposite to the direction of the second-stage cylinder for conveying the materials. Lime milk obtained by digestion in the first-stage cylinder enters the second-stage cylinder. The second-stage cylinder is provided with a second rotating shaft therein. The second rotating shaft is provided with blades. The second rotation shaft rotates counterclockwise (or clockwise). The lime milk, the coke powder and the fine iron powder are stirred and mixed by blades on a second rotating shaft and are simultaneously conveyed towards the direction of a discharge port of the second-stage cylinder.
Preferably, the second rotation shaft is eccentrically disposed.
Preferably, the cylinder of the second-stage cylinder is of a rotary structure. The second-stage cylindrical body rotates in the direction opposite to the direction of the second rotation shaft. The lime cream, the coke powder and the fine iron powder are subjected to the shearing force generated by the opposite rotation of the cylinder body of the second-stage cylinder and the second rotating shaft in the second-stage cylinder to form convection and mixing, and the fine iron powder and the lime cream are coated on the surface of the coke powder.
Preferably, the ratio of the rotational speed of the second rotational shaft to the rotational speed of the barrel is 5-20:1, preferably 7-15:1, more preferably 8-10: 1.
In the present invention, in step 1): the weight ratio of the quicklime to the water is 1:0.5-5, preferably 1: 0.8-3; more preferably 1:1 to 2, still more preferably 1:1.2 to 1.8.
In the present invention, in step 2): the weight ratio of the lime milk to the fine iron powder is 1:0.2-2, preferably 1: 0.3-1.5; more preferably 1:0.4 to 1.0, still more preferably 1:0.5 to 0.8.
In the present invention, in step 2): the mass ratio of the total weight of the mixture of the fine iron powder and the lime milk to the coke powder is 1:0.2-2, preferably 1:0.4-1.5, more preferably 1:0.6-1.2, and further preferably 1: 0.8-1.
In the present invention, in step 1): the slaking time of the quicklime in the first-stage cylinder is 0.5-4min, preferably 0.8-3min, and more preferably 1-2 min.
In the present invention, in step 2): mixing lime milk, coke powder, fine iron powder and water in the second-stage cylinder for 1-6min, preferably 2-5min, and more preferably 3-4 min.
According to a second embodiment provided by the present invention, a process for sintering iron ore is provided.
An iron ore sintering process, comprising the steps of:
1) conveying quicklime into a first-stage cylinder, spraying water into the first-stage cylinder, and digesting the quicklime in the first-stage cylinder to obtain lime milk;
2) conveying the lime milk obtained in the step 1) to a second-stage cylinder, and conveying coke powder and fine iron powder to the second-stage cylinder; mixing the lime milk, the coke powder and the fine iron powder through a second-stage cylinder to form a fuel structure taking the coke powder as a core, hanging the lime milk into slurry and coating the fine iron powder;
3) mixing the fuel structure which is obtained in the step 2) and takes the coke powder as the core, the lime cream slurry and the iron concentrate powder as the coating with other iron-containing raw materials and a flux to obtain a sintering material, and conveying the sintering material to a sintering machine for sintering to obtain a sintering ore.
Preferably, the first-stage cylinder has a first rotary shaft provided therein. The first rotating shaft is provided with blades. The first rotation shaft rotates clockwise (or counterclockwise). The quicklime and water are stirred and mixed by the blades on the first rotating shaft. The quicklime and the water are digested and mixed in the first-stage cylinder, and are simultaneously conveyed towards the discharge opening of the first-stage cylinder.
Preferably, the second stage cylinder in step 2) is disposed directly below the first stage cylinder. The direction of the first-stage cylinder for conveying the materials is opposite to the direction of the second-stage cylinder for conveying the materials. Lime milk obtained by digestion in the first-stage cylinder enters the second-stage cylinder. The second-stage cylinder is provided with a second rotating shaft therein. The second rotating shaft is provided with blades. The second rotation shaft rotates counterclockwise (or clockwise). The lime milk, the coke powder and the fine iron powder are stirred and mixed by blades on a second rotating shaft and are simultaneously conveyed towards the direction of a discharge port of the second-stage cylinder.
Preferably, the second rotation shaft is eccentrically disposed.
Preferably, the cylinder of the second-stage cylinder is of a rotary structure. The second-stage cylindrical body rotates in the direction opposite to the direction of the second rotation shaft. The lime cream, the coke powder and the fine iron powder are subjected to the shearing force generated by the opposite rotation of the cylinder body of the second-stage cylinder and the second rotating shaft in the second-stage cylinder to form convection and mixing, and the fine iron powder and the lime cream are coated on the surface of the coke powder.
Preferably, the ratio of the rotational speed of the second rotational shaft to the rotational speed of the barrel is 5-20:1, preferably 7-15:1, more preferably 8-10: 1.
In the present invention, in step 1): the weight ratio of the quicklime to the water is 1:0.5-5, preferably 1: 0.8-3; more preferably 1:1 to 2, still more preferably 1:1.2 to 1.8.
In the present invention, in step 2): the weight ratio of the lime milk to the fine iron powder is 1:0.2-2, preferably 1: 0.3-1.5; more preferably 1:0.4 to 1.0, still more preferably 1:0.5 to 0.8.
In the present invention, in step 2): the mass ratio of the total weight of the mixture of the fine iron powder and the lime milk to the coke powder is 1:0.2-2, preferably 1:0.4-1.5, more preferably 1:0.6-1.2, and further preferably 1: 0.8-1.
In the present invention, in step 1): the slaking time of the quicklime in the first-stage cylinder is 0.5-4min, preferably 0.8-3min, and more preferably 1-2 min.
In the present invention, in step 2): the mixing time of the lime milk, the coke powder and the fine iron powder in the second-stage cylinder is 1-6min, preferably 2-5min, and more preferably 3-4 min.
According to a third embodiment provided by the present invention, a coke powder pretreatment system for sintering is provided.
A coke powder pretreatment system for sintering or a system for treating the coke powder pretreatment process for sintering described in the first and second embodiments, the system comprising a primary drum, a secondary drum, a coke powder bin, an iron concentrate bin, a lime bin, and a conveying device. The lime bin is connected with the feeding hole of the first-stage cylinder through a conveying device. The discharge hole of the first-stage cylinder is connected with the lime milk feed inlet of the second-stage cylinder through a conveying device. The coke powder bin and the iron fine powder bin are connected with the material feeding port of the second-stage cylinder through respective conveying devices. A water spraying device is arranged in the first-stage cylinder.
Preferably, a first spiral sealing device is arranged above the feeding hole of the first-stage cylinder. A first spiral shaft is arranged in the first spiral sealing device. A first rotating shaft is arranged in the first-stage cylinder, and blades are arranged on the first rotating shaft. The discharge hole of the lime bin is connected to the first spiral sealing device through a conveying device.
Preferably, the second stage cylinder is disposed below the first stage cylinder. And a second spiral sealing device is arranged above the material feeding hole of the second-stage cylinder. A second spiral shaft is arranged in the second spiral sealing device. A second rotating shaft is arranged in the second-stage cylinder, and blades are arranged on the second rotating shaft. The discharge ports of the coke powder bin and the iron fine powder bin are connected to the second spiral sealing device through respective conveying devices.
Preferably, the second rotating shaft is eccentrically disposed, and a rotating direction of the second rotating shaft is opposite to a rotating direction of the first rotating shaft.
Preferably, the cylinder of the second-stage cylinder is of a rotary structure. The direction of rotation of the cylinder of the second-stage cylinder is opposite to the direction of rotation of the second rotary shaft.
Preferably, a valve is arranged at the discharge outlet of the lime bin or a conveying device connected with the lime bin.
Preferably, a weighing scale is arranged below the discharge hole of the coke powder bin.
Preferably, a valve is arranged at the discharge outlet of the iron fine powder bin or the conveying device connected with the iron fine powder bin.
Preferably, the conveying means is a conveyor belt, chute or chute.
Preferably, the water spraying device is connected with a water pipe. The water pipe is provided with a flowmeter.
In the invention, the quicklime is excessively digested through the first-stage cylinder to obtain completely digested lime milk. Then in the second-stage cylinder, the lime milk, the coke powder and the fine iron powder obtained after the first-stage cylinder are mixed and stirred, and then the mixture passes through the second-stage cylinderAnd (3) processing the barrel, wherein the lime milk is coated on the outer wall of the coke powder, and the lime milk is mixed with fine iron powder to form a fuel structure which takes the coke powder as a core, is coated with lime milk slurry and is coated with fine iron powder. Thereby improving the burning environment of the coke powder in the sintering process, reducing the oxygen potential in the peripheral gas film when the coke powder is burnt, preventing the coke powder after surface pretreatment from being directly exposed in an oxygen-containing sintering airflow medium during the burning, and being beneficial to reducing the N element to NO in the fuelxConversion of (3), reduction of NOxThe amount of production of (c). In addition, the coke powder (namely the modified coke powder) pretreated by the method of the invention has the surface lime and fine iron powder which can rapidly generate calcium ferrite products during sintering, and the calcium ferrite products can effectively promote the generated NOxIs reversely reduced to N in the sintering process2。
In the invention, in order to ensure that digestion and stirring are uniformly mixed, a two-stage cylinder which is arranged up and down is adopted. And the rotating direction of the first rotating shaft in the first-stage cylinder is opposite to the direction of the second rotating shaft in the second-stage cylinder, and the material conveying direction of the first-stage cylinder is opposite to the material conveying direction of the second-stage cylinder, so that the materials are uniformly mixed, and the lime milk and the fine iron powder can be uniformly coated on the surface of the coke powder.
Preferably, the second rotating shaft in the second-stage cylinder is arranged to be in an eccentric structure, so that the mixing effect of the lime milk, the coke powder and the fine iron powder in the second-stage cylinder is better facilitated, and meanwhile, a fuel structure taking the coke powder as a core, hanging the lime milk into slurry and wrapping the fine iron powder is prepared.
Preferably, in order to improve the coating effect of the lime milk and the fine iron powder on the coke powder, the cylinder body of the second-stage cylinder is designed to be a rotating structure, and the rotating direction of the cylinder body of the second-stage cylinder is opposite to the direction of the second rotating shaft. The lime milk, the coke powder and the fine iron powder can rotate and also can revolve in the second-stage cylinder, so that the lime milk, the coke powder and the fine iron powder are subjected to the shearing force generated by the opposite rotation of the cylinder body of the second-stage cylinder and the second rotating shaft in the second-stage cylinder to form convection and mixing, and the fine iron powder and the lime milk are coated on the surface of the coke powder. After the second-stage cylinder is used for treatment, due to the fact that the lime cream has extremely high viscosity, when other sintering raw materials (iron-containing raw materials, flux and the like) are added subsequently, the modified and pretreated coke powder can be bonded with the other sintering raw materials, the granulation effect is improved, and the improvement of the sintering product quality is facilitated.
In the invention, coke powder with poor hydrophobicity is subjected to surface modification by adopting lime milk with strong viscosity generated by slaking quicklime in a first-stage cylinder through pretreatment of the coke powder, and a small amount of fine iron powder is adhered to the surface of the coke powder to form a fuel structure taking the coke powder as a core, hanging lime milk and coating the fine iron powder. And uniformly mixing and granulating the pretreated coke powder with the sintering mixture, and conventionally sintering the pelletized pellets. The coke powder pretreated by the method is coated with a layer of lime milk and fine iron powder on the outer surface, so that the coke powder is not directly exposed to an oxygen-containing sintering airflow medium during combustion, and NO is reducedxGenerating; in addition, the lime milk and the iron ore powder on the surface of the coke powder quickly generate calcium ferrite products during sintering, thereby promoting NOxReduction to N2Reduction of NOxThe amount of production of (c).
The developed pretreated coke powder is used for sintering to form a new sintering process, which comprises the following steps: firstly, sufficiently stirring and digesting certain amount of quicklime and tap water in a first-stage cylinder to prepare lime milk, then mixing the lime milk, fine iron powder and coke powder in a second-stage cylinder, sufficiently stirring the mixture by the second-stage cylinder, finally, performing surface pretreatment on the coke powder with poor hydrophobicity by using the lime milk with strong viscosity generated by over-digestion of the quicklime, and adhering a small amount of fine iron powder on the surface of the coke powder to form a novel fuel structure which takes the coke powder as a core, coats the lime milk with slurry and is coated by the fine iron powder. The pretreated coke powder and the rest sintering mixture (comprising the rest quick lime for sintering, the rest water, other flux and iron-containing raw materials) enter a primary roller or a powerful mixer (preferably the powerful mixer) to be mixed uniformly, then enter a secondary roller to be granulated similar to the conventional sintering process, and the granulated pellets are arranged on a sintering machine trolley to be sintered.
In the new process, all the coke powder for sintering is subjected to surface pretreatment. In order to consider the problem of transportation of the pretreated coke powder to the next process (mixing with other sintering mixture), the ratio of the lime milk amount to the coke powder amount is required to be not too high, otherwise, the pretreated coke powder can generate the phenomenon of excessive humidity and water flowing in the belt transportation process; meanwhile, in order to ensure the effect of coke powder pretreatment on reducing the generation amount of sintered nitrogen oxides, the ratio of the lime milk amount to the coke powder amount is required to be not too low. According to experimental researches, the ratio of the weight sum of the primarily preferred mixture of the fine iron powder and the lime milk to the mass of the coke powder in the coke powder surface pretreatment system is 1:0.2-2, preferably 1:0.4-1.5, more preferably 1:0.6-1.2, and further preferably 1: 0.8-1. The proper proportion of the raw lime amount and the water amount is mainly determined on the premise of ensuring the fluidity of the lime milk, and the serious problems that the lime milk preparation system and the lime milk transportation system are blocked or the coke powder surface is not pretreated effectively and the like are caused due to the fact that the water amount is too small; and the water adding amount is too much, so that on one hand, the problem of excessive wetting and water flowing of the pretreated coke powder can occur, and on the other hand, the phenomenon that water is unavailable in the subsequent mixing and granulating processes can occur, so that the original material water balance is damaged. Through experimental research, lime with different activity degrees needs different water amounts for preparing lime milk with the same fluidity, and the primarily preferred ratio of the raw lime amount to the water amount is 1:0.5-5, preferably 1: 0.8-3; more preferably 1:1 to 2, still more preferably 1:1.2 to 1.8. Wherein the ratio of the primarily preferred lime milk amount to the iron concentrate amount is 1:0.2-2, preferably 1: 0.3-1.5; more preferably 1:0.4 to 1.0, still more preferably 1:0.5 to 0.8. The amount of the iron fine powder is ensured to be as much as possible that the molar ratio of calcium to iron in the substances coated on the surface of the coke powder is more than 1:1, and calcium ferrite substances are easily formed during sintering; on the other hand, the amount of the iron powder is not too large, otherwise, the viscosity of the lime milk is reduced, and the effect of coke powder surface pretreatment is influenced.
In the invention, the coke powder surface pretreatment system mainly comprises a quicklime bin, a coke powder bin, an iron fine powder bin, a first-stage cylinder, a second-stage cylinder and the like. The quicklime from the quicklime bin is quantitatively conveyed to a belt scale by a screw feeder, and enters a first-stage cylinder for digestion after being accurately weighed (or the adding amount of the quicklime is controlled by a valve).
The coke powder from the coke powder bin is quantitatively supplied into the second-stage cylinder by a weighing scale, and is fully stirred and uniformly mixed with the lime milk from the first-stage cylinder. The barrel body of the second-stage cylinder and the blades on the second stirring shaft rotate reversely, so that the fine iron powder and the lime milk are uniformly coated on the surface of the coke powder under the drive of revolution and rotation, and the pretreated coke powder and the coke powder are not agglomerated. The pretreated coke powder and the rest sintering mixture (comprising the rest quick lime for sintering, the rest water, other flux and iron-containing raw materials) are sequentially conveyed to the procedures of uniformly mixing and granulating by an adhesive tape machine, the procedures are similar to the conventional sintering process, and the granulated pellets are arranged on a sintering machine trolley for sintering.
In the invention, a valve and a first spiral sealing device are arranged at the lower part of the discharge hole of the quicklime bin (above the feed inlet of the first-stage cylinder), so that the quicklime can be accurately and quantitatively conveyed into the first-stage cylinder. A valve is arranged below the iron fine powder bin, so that the iron fine powder can be conveniently and quantitatively conveyed into the second-stage cylinder. The lower part of the discharge hole of the coke powder bin is provided with a weighing scale, so that the coke powder can be conveniently and quantitatively conveyed into the second-stage cylinder. The flowmeter is arranged on the water pipe, so that quantitative water can be conveniently added into the first-stage cylinder. The arrangement of each device in the system can quantitatively and properly add materials, so that the added materials can be proportioned as required, and the pretreated coke powder with better effect can be obtained.
In the invention, the coke powder is pretreated, so that a layer of fine iron powder is adhered to the surface of the coke powder by virtue of the viscosity of the lime milk, the coke powder is prevented from being directly exposed to an oxygen-containing sintering airflow medium during combustion, and the reduction of NO from fuel NxThe conversion of (a). Meanwhile, the lime milk and the fine iron powder on the surface of the coke powder can quickly generate a calcium ferrite product during sintering, and the calcium ferrite product can promote the generated NOxIs reversely reduced to N2Further reduction of NOxThe amount of production of (c).
In the invention, the lime milk for pretreating the coke powder is obtained by over-digesting the quick lime, and the lime milk is an emulsion-shaped sticky matter with extremely strong viscosity. In the first step of the invention, the ratio of the quicklime to the water is controlled to be 1:0.5-5, preferably 1: 0.8-3; more preferably 1:1-2, inIn one step, the preferable range is 1:1.2-1.8, the moisture of the added wetting amount in the prior art is changed, and the using amount of water is increased, so that the quicklime is completely digested to form the lime milk in an emulsion state. This feature of the invention brings about a very strong effect: the lime milk and the fine iron powder are wrapped outside the coke powder, so that the coke powder is prevented from being directly exposed in an oxygen-containing sintering airflow medium, and NO is reducedxAnd (4) generating. In addition, because the coke powder is hydrophobic small particles, in the prior art, the coke powder is extremely difficult to be mixed with other sintering raw materials into granules, and the coke powder always exists in the sintering raw materials independently, so that the granulating effect of the mixture is poor, and the air permeability of a sintering material layer is poor. According to the invention, the periphery of the pretreated coke powder is wrapped with a layer of lime milk, the lime milk has extremely strong viscosity, and when other sintering raw materials are added subsequently, the coke powder can be bonded with other sintering raw materials, so that the granulation effect is improved, and the sintering production quality is improved.
In the invention, the fuel (such as coke powder or coal powder) for sintering is completely pretreated and then added into other residual sintering materials, wherein the residual sintering materials do not contain coke powder, and the concentration of nitrogen oxides in the sintering flue gas is greatly reduced by pretreating all the coke powder. Through experimental research, NO in sintering flue gas is obtained after sintering by adopting the methodxThe generation amount and concentration of the nitrogen oxide are reduced by 20-40%, the emission of nitrogen oxide is greatly reduced, and the environment is protected.
In the invention, a first screw shaft in a first screw sealing device is used for quantitatively conveying quicklime; meanwhile, the function of sealing the first-stage cylinder is achieved; and the reverse channeling of dust and water vapor generated in the process of slaking the quicklime in the first-stage cylinder is avoided.
In the invention, a second screw shaft in the second screw sealing device is used for conveying coke powder and fine iron powder; meanwhile, the function of sealing the second-stage cylinder is achieved; and the reverse channeling of dust and water vapor generated in the mixing process of the lime milk, the coke powder and the fine iron powder in the second-stage cylinder is avoided.
In the invention, the second rotating shaft is eccentrically arranged, and the rotating direction of the second rotating shaft is opposite to that of the first rotating shaft; the purpose of this design is in order to strengthen stirring, the mixed effect of second level drum, through changing direction of rotation and eccentric settings for lime milk, burnt powder, fine iron powder receive unequal stirring power in the different positions of second level drum, and self produces the centrifugal force of equidimension not simultaneously, has improved the effect of stirring and mixing.
In the invention, the cylinder body of the second-stage cylinder is of a rotating structure, and the rotating direction of the cylinder body of the second-stage cylinder is opposite to that of the second rotating shaft; the purpose of this design is: the second-stage cylinder can rotate and also can revolve. The lime milk, the coke powder and the fine iron powder are subjected to shearing force in the second-stage cylinder to form mutual convection, the mixture is more sufficient, and the fine iron powder and the lime milk are coated on the surface of the coke powder.
In the present invention, the length of the first-stage cylinder is 2 to 20m, preferably 4 to 15m, more preferably 5 to 10m, and still more preferably 6 to 8 m.
The diameter of the inner cavity of the first-stage cylinder is 0.2 to 10m, preferably 0.5 to 8m, more preferably 0.8 to 5m, and still more preferably 1 to 3 m.
The length of the second-stage cylinder is 2 to 20m, preferably 4 to 15m, more preferably 5 to 10m, and still more preferably 6 to 8 m.
The diameter of the inner cavity of the second-stage cylinder is 0.2 to 10m, preferably 0.5 to 8m, more preferably 0.8 to 5m, and still more preferably 1 to 3 m.
The cross section of the inner cavities of the first-stage cylinder and the second-stage cylinder is circular or elliptical, and circular is preferred.
Compared with the prior art, the technical scheme of the invention has the following beneficial technical effects:
1. the method utilizes the lime milk with extremely strong viscosity generated by over-digestion of the quicklime to carry out surface pretreatment on the coke powder with relatively poor hydrophobicity, and a small amount of fine iron powder is adhered to the surface of the coke powder to form a novel fuel structure which takes the coke powder as a core, and is coated with the lime milk and the fine iron powder; the coke powder after surface pretreatment can not be directly exposed to oxygen-containing sintering airflow medium during combustion, so that NO is reducedxGenerating;
2. by the method of the inventionThe treated coke powder, lime on the surface of the coke powder and fine iron powder rapidly generate calcium ferrite products during sintering, thereby promoting the generated NOxIs reversely reduced to N2；
3. According to the invention, a cylinder is adopted to pretreat coke powder, excessive water is added into a first-stage cylinder to obtain lime milk digested excessively, then a second-stage cylinder is adopted to mix the lime milk, the coke powder and fine iron powder, stirring is more sufficient and uniform, and a novel fuel structure which is uniformly distributed and takes the coke powder as a core, and is coated with lime milk and fine iron powder is obtained;
4. the lime milk and fuel pretreatment method adopts two-stage cylinders arranged up and down to prepare the lime milk and fuel pretreatment, wherein the rotating shaft and the cylinder body in the second-stage cylinder rotate oppositely, so that the mixture is subjected to shearing force in the second-stage cylinder to form mutual convection, the mixing is more sufficient, the fine iron powder and the lime milk are wrapped on the surface of the coke powder, and the wrapping effect is better.
The coke powder pretreated by the technology of the invention is used in the sintering process, aiming at the current national pollutant discharge standard (less than or equal to 300 mg/m)3) The sintering flue gas can be discharged outside only after being purified by a desulfurization system; aiming at the pollutant emission standard (less than or equal to 100 mg/m) of the new future country3) The sintering flue gas can reach the standard only by configuring a single-tower type active carbon flue gas purification device.
In conclusion, the technology of the invention effectively solves the defects and shortcomings of the prior art, has low manufacturing cost, and can be expected to have high application value in the future market.
Drawings
FIG. 1 is a flow chart of a coke powder pretreatment process for sintering according to the present invention;
FIG. 2 is a flow diagram of an iron ore sintering process according to the present invention;
FIG. 3 is a schematic view of a coke powder pretreatment system for sintering according to the present invention;
FIG. 4 is a schematic view of the digestion and coating apparatus of the treatment system of the present invention.
Reference numerals:
1: a first stage cylinder; 101: a first rotating shaft; 102: a feed inlet of the first stage cylinder; 103: a discharge port of the first-stage cylinder; 104: a water spraying device; 2: a second stage cylinder; 201: a second rotation shaft; 202: a barrel of a second stage cylinder; 203: a lime milk feed inlet of the second stage cylinder; 204: a material feed port of the second stage cylinder; 3: a coke powder bin; 4: an iron fine powder bin; 5: a lime bin; 6: a conveying device; 7: a first spiral sealing device; 701: a first screw shaft; 8: a second spiral seal; 801: a second screw shaft; 9: a blade; 10: a flow meter; l1: a water pipe.
Detailed Description
According to the embodiment provided by the invention, a coke powder pretreatment system for sintering is provided.
A coke powder pretreatment system for sintering or a system for treating the coke powder pretreatment process for sintering described in the first and second embodiments includes a primary cylinder 1, a secondary cylinder 2, a coke powder bin 3, an iron concentrate bin 4, a lime bin 5, and a conveying device 6. The lime bin 5 is connected to the feed inlet 102 of the first stage cylinder 1 by a conveying device 6. The discharge hole 103 of the first-stage cylinder 1 is connected with the lime milk feed inlet 203 of the second-stage cylinder 2 through the conveying device 6. The coke powder bin 3 and the iron powder bin 4 are connected with the material feeding port 204 of the second-stage cylinder 2 through respective conveying devices 6. A water spray device 104 is arranged in the first-stage cylinder 1.
Preferably, a first spiral sealing device 7 is arranged above the feeding hole 102 of the first-stage cylinder 1. The first screw sealing device 7 is provided with a first screw shaft 701 therein. The first-stage cylinder 1 is provided with a first rotating shaft 101, and the first rotating shaft 101 is provided with blades 9. The discharge opening of the lime bin 5 is connected to a first screw sealing device 7 by means of a conveying device 6.
Preferably, the second stage cylinder 2 is disposed below the first stage cylinder 1. And a second spiral sealing device 8 is arranged above the material inlet 204 of the second-stage cylinder 2. A second screw shaft 801 is arranged in the second screw sealing device 8. A second rotating shaft 201 is provided in the second-stage cylinder 2, and the second rotating shaft 201 is provided with blades 9. The discharge openings of the coke powder bin 3 and the iron powder bin 4 are connected to a second spiral sealing device 8 through respective conveying devices 6.
Preferably, the second rotating shaft 201 is eccentrically disposed, and a rotating direction of the second rotating shaft 201 is opposite to a rotating direction of the first rotating shaft 101.
Preferably, the cylinder 202 of the second stage cylinder 2 is of a rotary construction. The direction of rotation of the cylinder 202 of the second-stage cylinder is opposite to the direction of rotation of the second rotary shaft 201.
Preferably, a valve is arranged at the discharge outlet of the lime bin 5 or the conveying device 6 connected with the lime bin 5.
Preferably, a weighing scale is arranged below the discharge hole of the coke powder bin 3.
Preferably, a valve is arranged at the discharge outlet of the iron fine powder bin 4 or the conveying device 6 connected with the iron fine powder bin 4.
Preferably, the conveying device 6 is a conveyor belt, chute or chute.
Preferably, the water spray device 104 is connected to the water pipe L1. The flow meter 10 is provided on the water pipe L1.
Example 1
As shown in fig. 1, a coke powder pretreatment process for sintering comprises the following steps:
1) conveying quicklime into the first-stage cylinder 1, spraying water into the first-stage cylinder 1, and digesting the quicklime in the first-stage cylinder 1 to obtain lime milk;
2) conveying the lime milk obtained in the step 1) into a second-stage cylinder 2, conveying coke powder and fine iron powder into the second-stage cylinder 2, and mixing the lime milk, the coke powder and the fine iron powder in the second-stage cylinder 2 to form a fuel structure taking the coke powder as a core, coating lime milk and coating fine iron powder.
Wherein: in step 1): the weight ratio of the quicklime to the water is 1: 1.5; in step 2): the weight ratio of the lime milk to the fine iron powder is 1:0.5, and the weight ratio of the total weight of the mixture of the fine iron powder and the lime milk to the mass of the coke powder is 1:1.
In step 1): slaking time of quicklime in the first-stage cylinder 1 is 2min, and in the step 2): the mixing time of the lime milk, the coke powder and the fine iron powder in the second-stage cylinder 2 is 4 min.
Example 2
Example 1 was repeated except that the first-stage cylinder 1 was provided with the first rotating shaft 101 therein. The first rotary shaft 101 is provided with blades. The first rotation shaft 101 rotates clockwise. The quicklime and water are stirred and mixed by the blades on the first rotating shaft 101. The quicklime and the water are digested and mixed in the first-stage cylinder 1 and are simultaneously conveyed towards the discharge opening of the first-stage cylinder 1.
The second-stage cylinder 2 in the step 2) is arranged right below the first-stage cylinder 1. The direction of material conveying of the first-stage cylinder 1 is opposite to the direction of material conveying of the second-stage cylinder 2. The lime milk obtained by digestion in the first stage cylinder 1 enters the second stage cylinder 2. The second-stage cylinder 2 has a second rotary shaft 201 provided therein. The second rotating shaft 201 is provided with blades. The second rotating shaft 201 rotates in a counterclockwise direction. The lime milk, the coke powder and the fine iron powder are stirred and mixed by the blades on the second rotating shaft 201 and are simultaneously conveyed towards the discharge port of the second-stage cylinder 2.
Example 3
Embodiment 2 is repeated except that the second rotating shaft 201 is eccentrically disposed. The cylinder 202 of the second stage cylinder 2 is of a rotary construction. The direction of rotation of the cylinder of the second stage cylinder 2 is opposite to the direction of the second rotation shaft 201. The lime cream, the coke powder and the fine iron powder are subjected to the shearing force in the second-stage cylinder 2, which is generated by the rotation of the cylinder body 202 of the second-stage cylinder and the second rotating shaft 201 in the opposite directions, to form convection and mixing, and the fine iron powder and the lime cream are coated on the surface of the coke powder. The ratio of the rotational speed of the second rotating shaft 201 to the rotational speed of the cylinder 202 was 9: 1.
Example 4
Example 3 was repeated except that in step 1): the weight ratio of the quicklime to the water is 1: 2; in step 2): the weight ratio of the lime milk to the fine iron powder is 1:1, and the weight ratio of the total weight of the mixture of the fine iron powder and the lime milk to the mass of the coke powder is 1: 1.2.
In step 1): slaking time of quicklime in the first-stage cylinder 1 is 0.8min, and in the step 2): the mixing time of the lime milk, the coke powder, the fine iron powder and the water in the second-stage cylinder 2 is 2 min.
The ratio of the rotational speed of the second rotating shaft 201 to the rotational speed of the cylinder 202 is 7: 1.
Example 5
As shown in fig. 2, the iron ore sintering process adopts the fuel structure which is obtained in example 1 and takes coke powder as the core, lime milk is coated with slurry, and fine iron powder is coated with other iron-containing raw materials and a flux to be mixed to obtain a sintering material, and the sintering material is conveyed to a sintering machine to be sintered to obtain a sintering ore.
Example 6
The process adopts the fuel structure which is obtained in the embodiment 4 and takes the coke powder as the core, the lime milk slurry and the iron concentrate powder as the coating, and mixes the fuel structure with other iron-containing raw materials and a flux to obtain a sintering material, and the sintering material is conveyed to a sintering machine for sintering to obtain a sintering ore.
Example 7
As shown in figure 3, the system for pretreating the coke powder for sintering comprises a first-stage cylinder 1, a second-stage cylinder 2, a coke powder bin 3, fine iron powder 4, a lime bin 5 and a conveying device 6. The lime bin 5 is connected to the feed inlet 102 of the first stage cylinder 1 by a conveying device 6. The discharge hole 103 of the first-stage cylinder 1 is connected with the lime milk feed inlet 203 of the second-stage cylinder 2 through the conveying device 6. The coke powder bin 3 and the fine iron powder 4 are connected with a material inlet 204 of the second-stage cylinder 2 through respective conveying devices 6. A water spray device 104 is arranged in the first-stage cylinder 1.
Example 8
Example 7 was repeated except that the first spiral sealing device 7 was provided above the feed inlet 102 of the first stage cylinder 1. The first screw sealing device 7 is provided with a first screw shaft 701 therein. The first-stage cylinder 1 is provided with a first rotating shaft 101, and the first rotating shaft 101 is provided with blades 9. The discharge opening of the lime bin 5 is connected to a first screw sealing device 7 by means of a conveying device 6.
The second stage cylinder 2 is disposed below the first stage cylinder 1. And a second spiral sealing device 8 is arranged above the material inlet 204 of the second-stage cylinder 2. A second screw shaft 801 is arranged in the second screw sealing device 8. A second rotating shaft 201 is provided in the second-stage cylinder 2, and the second rotating shaft 201 is provided with blades 9. The discharge openings of the coke powder bin 3 and the iron powder bin 4 are connected to a second spiral sealing device 8 through respective conveying devices 6.
Example 9
Embodiment 8 is repeated except that the second rotating shaft 201 is eccentrically disposed, and the rotating direction of the second rotating shaft 201 is opposite to the rotating direction of the first rotating shaft 101. The cylinder 202 of the second stage cylinder 2 is of a rotary construction. The direction of rotation of the cylinder 202 of the second-stage cylinder is opposite to the direction of rotation of the second rotary shaft 201.
Example 10
Example 9 is repeated, except that the conveying device 6 connected to the lime bin 5 is provided with a valve. A weighing scale is arranged below the discharge hole of the coke powder bin 3. A valve is arranged on the conveying device 6 connected with the iron fine powder bin 4. The conveying device 6 is a chute. The water jet device 104 is connected to a water pipe L1. The flow meter 10 is provided on the water pipe L1.
Example 11
Coke powder pretreated using the system described in example 10 was used in a sintering process comprising:
1) conveying 8t/h of quicklime into the first-stage cylinder 1, spraying water into the first-stage cylinder 1 at a speed of 12t/h, and digesting the quicklime in the first-stage cylinder 1 to obtain lime milk;
2) conveying the lime milk obtained in the step 1) into a second-stage cylinder 2, and simultaneously conveying all 30t/h of coke powder and 10t/h of fine iron powder used for sintering production into the second-stage cylinder 2; mixing the lime milk, the coke powder and the fine iron powder through a second-stage cylinder 2 to form a fuel structure taking the coke powder as a core, coating the lime milk with slurry and coating the fine iron powder;
3) uniformly mixing the pretreated coke powder prepared in the step 2) with other 800t/h sintering materials, granulating, and arranging the granulated sintering materials on a sintering machine trolley for sintering;
example 12
Example 11 was repeated, except that in step 1), quicklime was added in a weight of 4t/h and water was added in a weight of 8.5 t/h. In the step 2), the weight of the added iron ore powder is 12.5t/h, and the weight of the added coke powder is 30 t/h.
Comparative example 1
1) Firstly digesting 2.7t/h of quicklime with 4t/h of water, and then pretreating part of 10t/h of coke powder used for sintering production with 3.3t/h of iron ore concentrate to obtain pretreated coke powder;
2) uniformly mixing the pretreated coke powder obtained in the step 1) with the rest sintering material, granulating, and arranging the granulated sintering material on a sintering machine trolley for sintering;
wherein: the residual sintering material comprises 20t/h of coke powder and the rest of quick lime, water, flux and iron-containing raw materials.
Comparative example 2
1) All sintering materials are directly mixed and granulated and then are arranged on a sintering machine trolley for sintering;
wherein: the total sintering material refers to 30t/h of coke powder and sintering materials such as quick lime, water, flux, iron-containing raw materials and the like.
The concentration of nitrogen oxides in the sintering flue gas drawn from the sintering machine after sintering in examples 11 and 12 and comparative examples 1 and 2 was measured, and the following table was used:
Figure BDA0001968211370000141
the raw fuel condition 1 means that the concentration of nitrogen oxides in the flue gas discharged by the sintering process is higher than 300mg/m in the prior art3The process conditions of (1). The raw fuel condition 2 means that the concentration of nitrogen oxides in the flue gas discharged by the sintering process is higher than 200mg/m in the prior art3Less than 300mg/m3The process conditions of (1). In the prior art, two sets of standards are adopted; according to the current standard requirement, all sintering machines execute SO2The concentration is 200mg/m3、NOxThe concentration is 300mg/m3Emission limit of (d); some local standards are more strict, such as industrial kiln NO of Shanghai cityxThe emission limit is 200mg/m3。
The pretreated coke powder provided by the invention is adopted, and the existing sintering machine is adopted for sintering, aiming at the current national pollutant emission standard (the concentration of nitrogen oxide is less than or equal to 300 mg/m)3) The sintering flue gas can be discharged outside only after being purified by a desulfurization system; aiming at the pollutant emission standard (the concentration of nitrogen oxide is less than or equal to 100 mg/m) of the new country in the future3) The sintering flue gas can reach the standard only by configuring a single-tower type active carbon flue gas purification device.

Claims (20)

1. A coke powder pretreatment process for sintering comprises the following steps:
1) conveying quicklime into the first-stage cylinder (1), spraying water into the first-stage cylinder (1), and digesting the quicklime in the first-stage cylinder (1) to obtain lime milk;
2) conveying the lime milk obtained in the step 1) into a second-stage cylinder (2), conveying coke powder and fine iron powder into the second-stage cylinder (2), and mixing the lime milk, the coke powder and the fine iron powder in the second-stage cylinder (2) to form a fuel structure taking the coke powder as a core, coating lime milk with slurry and coating the fine iron powder;
wherein: in the step 1), a first rotating shaft (101) is arranged in the first-stage cylinder (1), and blades are arranged on the first rotating shaft (101); the first rotating shaft (101) rotates clockwise; stirring and mixing quicklime and water by a blade on a first rotating shaft (101); slaking and mixing quicklime and water in the first-stage cylinder (1) and simultaneously conveying the slaked quicklime and water to the direction of a discharge port of the first-stage cylinder (1); in the step 2), the second-stage cylinder (2) is arranged right below the first-stage cylinder (1), and the direction of conveying materials by the first-stage cylinder (1) is opposite to the direction of conveying materials by the second-stage cylinder (2); lime milk obtained by digestion of the first-stage cylinder (1) enters the second-stage cylinder (2); a second rotating shaft (201) is arranged in the second-stage cylinder (2), blades are arranged on the second rotating shaft (201), and the second rotating shaft (201) rotates anticlockwise; the lime milk, the coke powder and the fine iron powder are stirred and mixed by blades on a second rotating shaft (201) and are simultaneously conveyed towards the direction of a discharge port of a second-stage cylinder (2).
2. An iron ore sintering process, comprising the steps of:
1) conveying quicklime into the first-stage cylinder (1), spraying water into the first-stage cylinder (1), and digesting the quicklime in the first-stage cylinder (1) to obtain lime milk;
2) conveying the lime milk obtained in the step 1) into a second-stage cylinder (2), conveying coke powder and fine iron powder into the second-stage cylinder (2), and mixing the lime milk, the coke powder and the fine iron powder in the second-stage cylinder (2) to form a fuel structure taking the coke powder as a core, coating lime milk with slurry and coating the fine iron powder;
3) mixing the fuel structure which is obtained in the step 2) and takes the coke powder as the core, the lime cream slurry and the iron concentrate powder as the coating with other iron-containing raw materials and a flux to obtain a sintering material, and conveying the sintering material to a sintering machine for sintering to obtain a sintering ore;
wherein: in the step 1), a first rotating shaft (101) is arranged in the first-stage cylinder (1), and blades are arranged on the first rotating shaft (101); the first rotating shaft (101) rotates clockwise; stirring and mixing quicklime and water by a blade on a first rotating shaft (101); slaking and mixing quicklime and water in the first-stage cylinder (1) and simultaneously conveying the slaked quicklime and water to the direction of a discharge port of the first-stage cylinder (1); in the step 2), the second-stage cylinder (2) is arranged right below the first-stage cylinder (1), and the direction of conveying materials by the first-stage cylinder (1) is opposite to the direction of conveying materials by the second-stage cylinder (2); lime milk obtained by digestion of the first-stage cylinder (1) enters the second-stage cylinder (2); a second rotating shaft (201) is arranged in the second-stage cylinder (2), blades are arranged on the second rotating shaft (201), and the second rotating shaft (201) rotates anticlockwise; the lime milk, the coke powder and the fine iron powder are stirred and mixed by blades on a second rotating shaft (201) and are simultaneously conveyed towards the direction of a discharge port of a second-stage cylinder (2).
3. The process according to claim 1 or 2, characterized in that: the second rotating shaft (201) is arranged eccentrically; and/or
The cylinder body (202) of the second-stage cylinder (2) is of a rotating structure; the rotating direction of the cylinder body of the second-stage cylinder (2) is opposite to the direction of the second rotating shaft (201); the lime milk, the coke powder and the fine iron powder are subjected to the shearing force in the second-stage cylinder (2) by the rotation of the cylinder body (202) of the second-stage cylinder and the second rotating shaft (201) in opposite directions to form convection and mixing, and the fine iron powder and the lime milk are coated on the surface of the coke powder.
4. The process according to claim 3, characterized in that: the ratio of the rotation speed of the second rotating shaft (201) to the rotation speed of the cylinder (202) is 5-20: 1.
5. The process according to claim 3, characterized in that: the ratio of the rotation speed of the second rotating shaft (201) to the rotation speed of the cylinder (202) is 7-15: 1.
6. The process according to claim 3, characterized in that: the ratio of the rotation speed of the second rotating shaft (201) to the rotation speed of the cylinder (202) is 8-10: 1.
7. The process according to any one of claims 1, 2, 4-6, wherein: in step 1): the weight ratio of the quicklime to the water is 1: 0.5-5; and/or
In step 2): the weight ratio of the lime milk to the fine iron powder is 1: 0.2-2; the mass ratio of the total weight of the mixture of the fine iron powder and the lime milk to the coke powder is 1: 0.2-2.
8. The process according to claim 3, characterized in that: in step 1): the weight ratio of the quicklime to the water is 1: 0.5-5; and/or
In step 2): the weight ratio of the lime milk to the fine iron powder is 1: 0.2-2; the mass ratio of the total weight of the mixture of the fine iron powder and the lime milk to the coke powder is 1: 0.2-2.
9. The process according to claim 7, characterized in that: in step 1): the weight ratio of the quicklime to the water is 1: 0.8-3; and/or
In step 2): the weight ratio of the lime milk to the fine iron powder is 1: 0.3-1.5; the mass ratio of the total weight of the mixture of the fine iron powder and the lime milk to the coke powder is 1: 0.4-1.5.
10. The process according to claim 8, characterized in that: in step 1): the weight ratio of the quicklime to the water is 1: 0.8-3; and/or
In step 2): the weight ratio of the lime milk to the fine iron powder is 1: 0.3-1.5; the mass ratio of the total weight of the mixture of the fine iron powder and the lime milk to the coke powder is 1: 0.4-1.5.
11. The process according to claim 9 or 10, characterized in that: in step 1): the weight ratio of the quicklime to the water is 1: 1-2; and/or
In step 2): the weight ratio of the lime milk to the fine iron powder is 1: 0.4-1.0; the mass ratio of the total weight of the mixture of the fine iron powder and the lime milk to the coke powder is 1: 0.6-1.2.
12. The process of any one of claims 1, 2, 4-6, 8-10, wherein: in step 1): slaking the quicklime in the first-stage cylinder (1) for 0.5-4 min; and/or
In step 2): the mixing time of the lime milk, the coke powder and the fine iron powder in the second-stage cylinder (2) is 1-6 min.
13. The process according to claim 3, characterized in that: in step 1): slaking the quicklime in the first-stage cylinder (1) for 0.5-4 min; and/or
In step 2): the mixing time of the lime milk, the coke powder and the fine iron powder in the second-stage cylinder (2) is 1-6 min.
14. The process according to claim 12, characterized in that: in step 1): slaking the quicklime in the first-stage cylinder (1) for 0.8-3 min; and/or
In step 2): the mixing time of the lime milk, the coke powder and the fine iron powder in the second-stage cylinder (2) is 2-5 min.
15. The process according to claim 13, characterized in that: in step 1): slaking the quicklime in the first-stage cylinder (1) for 0.8-3 min; and/or
In step 2): the mixing time of the lime milk, the coke powder and the fine iron powder in the second-stage cylinder (2) is 2-5 min.
16. The process according to claim 14 or 15, characterized in that: in step 1): slaking the quicklime in the first-stage cylinder (1) for 1-2 min; and/or
In step 2): the lime milk, the coke powder and the fine iron powder are mixed in the second-stage cylinder (2) for 3-4 min.
17. The utility model provides a burnt powder pretreatment systems for sintering which characterized in that: the system comprises a first-stage cylinder (1), a second-stage cylinder (2), a coke powder bin (3), an iron fine powder bin (4), a lime bin (5) and a conveying device (6); the lime bin (5) is connected with a feed inlet (102) of the first-stage cylinder (1) through a conveying device (6); the discharge hole (103) of the first-stage cylinder (1) is connected with the lime milk feed hole (203) of the second-stage cylinder (2) through a conveying device (6); the coke powder bin (3) and the iron fine powder bin (4) are connected with a material feeding hole (204) of the second-stage cylinder (2) through respective conveying devices (6); a water spraying device (104) is arranged in the first-stage cylinder (1);
wherein: a first spiral sealing device (7) is arranged above the feeding hole (102) of the first-stage cylinder (1), and a first spiral shaft (701) is arranged in the first spiral sealing device (7); a first rotating shaft (101) is arranged in the first-stage cylinder (1), and blades (9) are arranged on the first rotating shaft (101); a discharge hole of the lime bin (5) is connected to a first spiral sealing device (7) through a conveying device (6);
the second-stage cylinder (2) is arranged below the first-stage cylinder (1); a second spiral sealing device (8) is arranged above the material feeding hole (204) of the second-stage cylinder (2), and a second spiral shaft (801) is arranged in the second spiral sealing device (8); a second rotating shaft (201) is arranged in the second-stage cylinder (2), and blades (9) are arranged on the second rotating shaft (201); the discharge holes of the coke powder bin (3) and the iron fine powder bin (4) are connected to a second spiral sealing device (8) through respective conveying devices (6); the direction of rotation of the second rotating shaft (201) is opposite to the direction of rotation of the first rotating shaft (101).
18. The system of claim 17, wherein: the second rotating shaft (201) is arranged eccentrically; and/or
The cylinder (202) of the second-stage cylinder (2) has a rotating structure, and the rotating direction of the cylinder (202) of the second-stage cylinder is opposite to the rotating direction of the second rotating shaft (201).
19. The system according to claim 17 or 18, wherein: a valve is arranged at the discharge outlet of the lime bin (5) or on a conveying device (6) connected with the lime bin (5); a weighing scale is arranged below the discharge hole of the coke powder bin (3); a valve is arranged at the discharge outlet of the iron fine powder bin (4) or on a conveying device (6) connected with the iron fine powder bin (4).
20. The system of claim 19, wherein: the conveying device (6) is a conveyor belt, a chute or a chute; the water spraying device (104) is connected with a water pipe (L1), and a flowmeter (10) is arranged on the water pipe (L1).
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